Field of the Invention
The present invention relates to an array substrate having a switching element in a display device, and a display device including the same.
Description of the Background Art
The twisted nematic (TN) mode has been widely used as a display type of a liquid crystal display device that is a type of display device. Recently, the transverse electric field type liquid crystal display device has been proposed, in which a voltage is applied between the first and second electrodes provided in one substrate to generate an electric field almost parallel to the panel, whereby the liquid crystal molecules are driven horizontally. The transverse electric field type is advantageous in wider viewing angle, higher resolution and higher brightness and is now becoming mainstream particularly in middle or small sized panels such as smartphones and tablets.
Display types such as in plane switching (IPS) mode and fringe field switching (FFS) mode are known regarding the transverse electric field type liquid crystal display device. Of those, in the FFS mode, a first electrode and a second electrode that has slits are provided with an insulating film therebetween, where those electrodes serve as a pixel electrode and a counter electrode as appropriate. A transverse electric field can be generated in a liquid crystal layer located above the upper electrode through the slits thereof, which allows driving of liquid crystals in accordance with the transverse electric field.
For instance, Japanese Patent Application Laid-Open No. 2010-66396 discloses one example of the transverse electric field type liquid crystal display device. This liquid crystal display device includes a shield electrode provided to prevent the application of a DC electric field, which is generated in response to a high-voltage signal applied to a gate line, to the liquid crystals in its vicinity, and uses the shield electrode as a common wire for connecting common electrodes to the pixels.
In the liquid crystal display device of Japanese Patent Application Laid-Open No. 2010-66396, a second electrode corresponding to a pixel electrode and a drain electrode of a switching element are connected by a connection portion provided in a contact hole, and the connection portion is provided inside a region surrounded by two adjacent gate lines and two adjacent source lines. In this liquid crystal display device, unfortunately, an alignment film formed on a region near the connection portion cannot be rubbed reliably due to the unevenness of the connection portion (contact hole), resulting in a problem that the liquid crystals may not be driven. Under the present circumstances, the light passing through a region where the liquid crystals are not driven is blocked by a counter substrate disposed to face the array substrate. This results in narrower areas for pixels, causing a problem that a pixel aperture ratio decreases.